Data signals are generally stored on magnetic storage media as a series of sequential magnetic field transitions according to a digital code format which provides the best combination of low required storage system bandwidth and high storage medium density. Because the read signals from such magnetic media are pulses which represent the stored magnetic transitions, these read signals are characterized by a series of closely packed, generally spike-shaped pulses, which are then processed to reconstruct the written data. Of course, signal decoding is required, because the read signals only represent the transitions of magnetic states, not the coded data pulses themselves. Due to the bandwidth-limited nature of the read channel for the data storage system, the pulses comprising the read signal generally suffer distortion in both amplitude and phase. As a result of this distortion, the pulses have less amplitude, longer duration, and more asymmetry than if the read channel were not so bandwidth limited. This distortion can cause the read signal pulses to overlap each other to such an extent that they are unreadable.
To maximize the writing speed and information storage density in data storage drives, the read signal is equalized to correct the amplitude and phase distortion of the pulses so that the read signals are usable even with very high density storage media. Such equalization usually includes a multitap delay line or a cascaded, complex combination of inductors, capacitors and resistor networks.
Equalization networks generally require provisions for adjustment of their characteristics to account for component variations in the equalization network or the associated storage medium drive. Although tapped delay line equalizers are available with programmable characteristics, these units are bulky and expensive for commercial use. They also have unit-to-unit characteristic variations. Equalizers using discrete inductors, capacitors and resistors require component replacement to change characteristics, which is difficult and expensive. These equalizers also require delay lines to properly phase their equalizing signals.